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The invention concerns a leaf stripper, more specifically designed for vine leaf stripping.
Leaf stripping is a technique that consists of removing the leaves located in the fruit-bearing area of the plants. Made manually for years in some vineyards, this operation that is aimed at improving the quality of the harvest and at facilitating the thinning and picking work has become of growing interest with the development of mechanical leaf stripping.
The advantages of leaf stripping are multiple:
To promote grape bunch aeration so as to reduce rot.
To promote thinning in order to improve coloration (thicker grape skin).
To thin the plant cover in the fruit-bearing area for better penetration and location of treatments (botrytis-oidium-grey rot-grape caterpillars-mildew . . . ).
To improve ripening of the bunches through better sun exposure (heavier bunches, more developed aromas, and better health status of the harvest).
To favor access to the grape bunches so as to reduce labor time on manual operations such as thinning (xe2x88x9250%), manual harvesting (xe2x88x9230%-40%).
To reduce foliage so as to limit juice losses upon leaf aspiration from the remainder of the mechanically harvested vintage.
To facilitate drying when raining through better sun exposure and better aeration.
Leaf stripping thus proves to be a very interesting operation that responds well to the concern for task optimization and harvest quality.
Several machines and processes have been proposed to date and some of them are actually still used for the performance of this work.
In document FR-2,147,932, a leaf stripping device is described that uses a grid-type rotating cylindrical cage designed to roll over the plant cover and inside which a hollow cylinder provided with an opening is housed in a fixed manner. An aspirator mounted above the interior hollow cylinder is used to create, inside the latter, a negative pressure for the purpose of aspirating foliage leaves and blow them against the grid-type rotating cage. Rollers mounted on hinged brackets are arranged under pressure against the lateral surface of the cage and driven by the latter in a rotating manner. The leaves become jammed between the grid-type drum and the rollers and are torn from the branches under the tractive force resulting from the movement of the machine.
A priori, the principle of foliage stripping using the suction flow of a turbine through a grid-type rotating drum designed to pull and blow the leaves against the lateral surface of said drum seems judicious and power-efficient. However, it does not seem that the machine described in document FR-2,417,932 has been put on the market and to the knowledge of the deponent, no leaf stripper using that principle is marketed today.
The lack of success of this machine results certainly from the fact that the leaf tearing principle using friction rollers does not seem to be concretely applied for several reasons:
according to the description and the drawings of document FR-2,417,932, the hinged supports mounted on springs with rollers are intended to be positioned in the plant cover during operation; this arrangement is not applicable since said supports rub in the plant cover and hinder aspiration of the leaves as they push back the vegetation; it is not possible to position mechanical components in the plant cover beyond the wall of the rotating cage as they would telescope and be torn by various obstacles located in the axis of the vine row, such as stakes, wire tighteners and mainly posts;
because a relatively large effort is necessary to tear off leaves, it is unlikely that the effort created by the friction of the rollers on the drum is sufficient, especially if leaves or stems come between the cage wall and the rollers; and
this device, because of its location in relation to the plant cover and of its principle of severing leaves by tearing them off, can only cause plugging of the system through plant accumulation and damage the vine.
Document FR-2,390,084 describes a mechanical leaf stripper based on aspiration of the leaves with a turbine trough, a fixed grid, placed in front of the blades of the latter. The sharp blades of the turbine helix are used as means of severing the leaves. This system is well-known and most leaf strippers currently marketed are based on this principle.
These machines require a significant negative pressure to suck the leaves into the severing system made up by the turbine blades. These heavy and bulky machines are not equipped with a positioning system of the leaf stripping turbine in relation to the plant cover. The dexterity of the driver through the accuracy of his driving, necessarily at low speed, ensures the quality of stripping. This principle makes the stripping rate approximate and the injury rate to grape bunches high; the high suction power required for efficient stripping limits the speed of advance of the leaf stripper. The projections of shredded leaf particles and the dust raised by this type of machine are major disadvantages from a health point of view.
In document FR-2,406,384, a vine stripping machine is described that uses the blast of a fan through the plant cover to push the leaves through a grid-type rotating drum installed opposite thereto. The grid-type drum rolls over the plant cover while the leaves pushed by the blower through the rotating drum wall featuring horizontal bands are severed by cutters rotating inside it.
This solution has several disadvantages that probably explain its absence on the market, such as for example:
the difficulty to accurately channel the flow of air blowing through the plant cover, as stems, bunches and posts located between the fan and the cage or drum disturb and deviate the flow of air, thus preventing the leaves from entering the facing cage;
as described and drawn in document FR 2,406,384, the rotating cage that severs the leaves is mounted on the opposite side of the tractor; thus the operator has no visibility on the stripped area and this heavy and bulky architecture is thus inappropriate for this operation that requires continuous monitoring of the rate of leaves removed and of potential injuries to the grape bunches; and
finally, no device is provided for the discharge of the leaves cut inside in the cage and therefore rapid plugging can be expected due to the accumulation of cuttings inside the drum.
Document EP-0,597,253 describes very summarily an automatic vine leaf stripper comprising a foliage suction system using a centrifugal aspirator and a linear suction port, a leaf severing device with a reciprocating cutting blade placed close to said linear suction port, a roller installed in front of the suction system to be able to separate the leaves from the grape bunches and a conveyor belt placed in front of the stripping head whose moving speed is synchronized with the moving speed of the leaf stripper. This conveyor belt makes it possible to bear on the plant cover without causing any friction onto the grape bunches.
However, the leaf strippers currently marketed based on the arrangements described in that document are not equipped with the conveyor belt whose presence is the cause of disadvantages in view of which the result strived for seems secondary. In fact, the action of the belt upstream of the stripping head channels and probably pushes back leaves and bunches, but the belt stops in front of the suction port. When this vegetation passes in front of the suction port where the cutter blade is located, the belt no longer operates. The presence of this belt in front of the plant suction and severing system thus loses all efficiency with regard to the separation of leaves and bunches.
To separate the leaves from the bunches, a vertical roller is installed in the front of the suction and cutting system, between the conveyor belt and said system but after this roller goes by, nothing prevents the bunches from being sucked with the leaves and severed at the same time as said leaves.
In addition, the cutter bars with a reciprocating blade cause a relatively significant percentage of injuries to the bunches, especially with an assembly of the kind described in document EP-0,597,253.
In document EP-0,898,877, a vine leaf stripping device is described that uses the known principle of attracting the leaves with a suction port and severing them with a reciprocating blade. The originality of this device would lie in its capability to automatically position the stripping head in relation to the plant cover according to two planes through two electric sensors bearing on the row of vine, with one sensor controlling a hydraulic jack that adjusts the stripping depth, and the other sensor controlling a jack that tilts the stripping head to match the profile of the plant cover.
This principle of circling around the plant cover is interesting in theory; however, it has a few disadvantages, especially those related to the machine swings and plant cover unevenness that require inopportune and sudden changes of positions of the leaf stripping head. Because of the response times of the controls and the inertia generated by rapid changes of positions of the stripping head, such stripper is not suitable for bumpy terrains and can advance only at low speed. Its design is heavy and complex. In addition, for a construction of the type that is described in document EP-0,898,877, the use of a cutter bar comprising a reciprocating blade is likely to cause a not insignificant number of injuries to the grape bunches.
The purpose of the invention is among other things to eliminate the significant disadvantages of the strippers described in the prior art documents and/or currently available on the market.
To that effect, a machine was selected that comprises a leaf stripping device with a grid-type rotating drum, a suction means that permits to generate a suction air flow running through the perforated cylindrical side wall of said drum, and means to channel this air flow through a changing portion of said side wall.
According to that leaf suction principle through direct contact with the plant cover, it appears that the negative pressure flow necessary to snap and blow the leaves against the grid-type side wall of the rotating drum can be relatively small compared to conventional leaf strippers that stay relatively far from the plant cover, which requires a very high negative pressure and therefore a lot of power to draw the leaves into the stripping system.
According to a first characteristic arrangement of the invention, the actual leaf stripping system consists of a cutting means installed close to the suction portion of the side wall of the rotating drum and oriented parallel or roughly parallel to the axis of rotation of the latter.
Under another very important characteristic arrangement of the invention, the cutting means is arranged behind a diametrical plane of the rotating drum oriented perpendicular to the forward direction of the machine during operation.
Through the above characteristic arrangements, the machine is capable of performing a leaf stripping of a quality comparable to a trimming of the plant cover as the leaf stalks are cut and not shredded, contrary to the solutions previously proposed that remove the leaves by tearing them off using propellers or cutters or jam rollers.
After their stems are severed, the leaves remain stuck against the perforated side wall of the rotating drum and are driven out of the field of suction through the rotation of said wall. When the portion of the side wall plastered with cut leaves becomes isolated from the suction field by the suction flow deflector, the leaves, that are no longer subject to the air flow draw, fall by gravity. This result is another advantage as it eliminates the projections of shredded leaves likely to cause potential diseases due to the particles and dust propelled by the turbine blast onto the neighboring vine rows.
Under another characteristic arrangement of the invention, the stripping head or each head of the stripper comprises a guide track consisting of a grid-type endless belt wrapping, on one hand around the rotating suction drum, and, on the other hand, around a second drum installed in front of said suction drum, said perforated endless belt having on the side of the stripping head designed to be facing the plant cover during operation, a straight course, parallel to the axis of forward movement of the stripper so as to present a plane bearing surface.
The function of the perforated track thus made is to ensure proper guiding and stability of the stripping head on the plant cover. It provides a flexible bearing of the stripping head on the plant cover while avoiding the latter to be crushed because of its large contact surface.
According to a very important characteristic of the invention, the cutting means for the stripping head or for each stripping head consists of a helical cutter bar comprising, on one hand, a cutter screw consisting of a rotating cylindrical rod provided with a helical thread, featuring a cutting edge, and, on the other hand, a back blade consisting of a fixed cylindrical sleeve open laterally and inside which said cutting screw is housed, said sleeve being provided with spaced curved fingers forming as many back blades designed to cut off the leaf stalks and push back the grape bunches by preventing them from penetrating into the spaces bounded by said superposed fingers.
The main advantage of this helical cutter bar is, if not to totally eliminate every risk of injury to the bunches, at least to minimize the percentage of such injuries.
According to another embodiment of the invention, a cutting means is installed vertically in front of the stripping device and at a distance from it; this cutting means may consist of a reciprocating cutter bar or a similar device. This cutter bar is designed to trim the vine row over its total height so as to cut all leaves and stems the furthest from the fruit-bearing area. It is used to do a first rough cut: it trims down the plant cover in order to reduce the volume of leaves to be removed by the actual leaf stripping device.